Altair
What it is: Declarative visualization in Python using Vega-Lite. Describe what you want, not how to draw it.
What It Does Best
Simple, consistent API. Chart specification as JSON-like Python objects. Same pattern for every chart type.
Interactive by default. Tooltips, zooming, panning built-in. No extra code.
Reproducible. Declarative specs mean same code = same output. Easy to share and version control.
Pricing
Free. Open source, BSD license.
When to Use It
✅ Want simple, clean syntax
✅ Need quick exploratory plots
✅ Jupyter notebooks
✅ Prefer declarative over imperative
When NOT to Use It
❌ Extremely custom visualizations (use D3.js)
❌ Very large datasets (performance limits)
❌ Need publication-quality static images (Matplotlib better)
Bottom line: Matplotlib made declarative. Perfect middle ground between simplicity and interactivity. Great for data scientists who want clean code.